Freshwater mussels Lampsilis spp.
Mussels of the genus Lampsilis are widespread in North American streams. While the adult has a typical filtering life-style, the first larval stage - the glochidium - is a microscopic parasite of freshwater fishes. Young mussels attach to the gills of the fish host with their shell and suck their blood until they become large enough to move to the bottom of the stream.
The fascinating part of Lampsilis life-cycle is how they can reach the fish host. Indeed, the adults are typically sessile, they evolved a strategy to attract the fish host to increase transmission rate of the young mussels: like anglers, these mussels "fish" to get close to the host.
In these shellfishes, the mantle evolved to look like a prey fish of the host. The mimicry is improved by the contractions of the mantle that imitate the tail movements of the mimicked prey. When hungry host fish get to bite on the lure, the adult mussel ejects in its mouth hundreds of glochidia that attach to the gills as showed on this video:
sources for picture: modified from https://www.fws.gov/midwest/mussel/images/life_cycle_620.gif
and https://www.fws.gov/midwest/mussel/images/broken-rays_fishing_lure_620.jpg
and https://www.fws.gov/midwest/mussel/images/broken-rays_fishing_lure_620.jpg
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